Catalytic hydrocarbon conversion process in the presence of steam



Oct. 7, 1947.

LIGHT GASES A. SCHULZE El'AL CATALYTIG HYDROCARBON CONVERSION PROCESS IN THE PRESENCE OFl STAM FigLed May s, 1945 DILAIVLVD HEATER DILUENT Es., STEAM Patented Oct. 7, 1947 CATALYTIC HYDROCARBON CONVERSION PROCESS IN THE PRESENCE OF STEAM Walter A. Schulze and Carl J. Helmers, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Application May 3, 1943, Serial No. 485,482

2 Claims.

This invention relates to a process for converting relatively high or intermediate boiling petroleum fractions or similar materials of different origin into substantial yields of gasoline of high octane rating, high aromatic content and low olefin content. In one specific embodiment it relates to a process fo-r treating a petroleum distillate such as gas oil or naphtha of relatively wide boiling range wherein the gasoline produced by the catalytic cracking of the gas oil or naphtha is subjected to further catalytic treatment to produce a final product of high octane rating with a relatively high concentration of aromatic hydrocarbons and a relatively low content of olefin hydrocarbons and to produce concurrently normally gaseous hydrocarbons which contain a relatively high percentage of valuable olens.

An object of the invention is the production of high-octane aviation fuels with desirable combustion characteristics which contain a high concentration of aromatic hydrocarbons and a low concentration of undesirable unsaturated compounds.

A second object of the invention is the production of certain aromatic compounds such as benzene and certain important alkylbenzenes which may be segregated for special purposes. y

A further object of the invention is the production of high-octane aromatic gasolines with the concurrent production of normally gaseous hydrocarbons which contain a comparatively high percentage of olenic hydrocarbons.

The previous application of processes leading to the production of aromatic compounds has been, for the most part, in producing relatively minor amounts of aromatics in order to improve the antiknock properties of motor fuels. More recently, however, in view of the accelerated demand for high-octane aviation fuels, the formation of aromatic products is of interest in the production of such fuels. In addition to the use of aromatic compounds in aviation fuels, a further aspect is the segregation of certain of the aromatic components of such gasoline fractions such as benzene and certain alkylbenzenes for further treatment or uses.

For the most part, in the past, aromatization reactions have been described as occurring in thermal processes lunder severe temperature conditions. An objectionable feature of such processes is that large quantities of gaseous by-products are usually formed consisting in large part of methane and ethane which may be of little value except as fuel. Another disadvantage of the prevailing practice is the usual production of liquid by-products which interfere with the subsequent concentration or segregation of the aromatic constituents. v

Catalytic aromatization processes on the other hand, have heretofore operated at relatively lower temperatures under mild hydrogenating conditions which, while advantageous in other respects, limit the aromatic content obtainable and decrease the olefin content of the C3-C5 hydrocarbon by-products. In many instances these processes employ catalysts which are sensitiveto poisons and consequently require special adaptations of process conditions and reactivation methods as well as considerable expenditure for frequent catalyst reactivation and/or replacep ment. A further disadvantage of prior-,catalytic aromatization processes is the fact that few stocks are satisfactory for use as feed for these operations thus limiting the scope of application of the The gasolines produced directly by conventional thermal or catalytic cracking operations on charging stocks of the type described ordinarily kcontain a relatively high percentage of unsaturated hydrocarbons which raise the octane rating and sensitivity of the gasolines but at the same time tend to increase the gum-forming properties and acid-heat test and impart a lowered susceptibility to added antiknock agents. For these reasons such highly olefinic gasolinas are not ordinarily used in aviation fuels. It is known on the other hand, that gasolines with a relatively high content of aromatic compounds and a relatively low olefin content constitute good aviation fuel vblending stock because of their low acid heat test,

ture and relatively low pressures, such reactions as isomerization and cyclization may occur to form a gasoline which has a high content of aro- .matic hydrocarbons and a low content of oleiinic compounds in the gasoline boiling range. This catalytic treatment facilitates the production of a relatively large amount of aromatic compounds vwithout the attendant disadvantage of the formation of undesirable by-products.

We have found that the aromatization treatment as described above is particularly advantageous in producing a gasoline of improved octane rating which is suitable for use as an aviav tion fuel blending stock by virtue of its low acidheat properties and. low gum-forming tendencies and superior combustion characteristics. In addition, we have found that the aromatization treatment of the gasoline-type stock leads to the production of light gases which contain a relatively high percentage of useful olens. The invention, therefore, comprises a novel and advantageous series of steps to produce a final product With desirable characteristics.

We have further found that the catalytic treat-f ment of gasolines produced by one-pass, deep conversion of intermediateboiling productsr such as may be obtained by straight distillation of4 crude oil results in particularly efficient production of aromatic compounds. A specific embodiment of the invention, therefore, involves a two- ,l

vationthis particularV two-stage embodiment of the invention. It should be understood, however, that modifications and variations in the equipment may be made as' desired without departing fromthe scope of the invention.

With'reference-'novv tothe drawing, the'feed stock for the process, which may bea gas oil of rather wide boiling range such as that fraction -b'oili'ng between about-400 and '706F. which may be obtained'by the straight distillation of a crude oil'or mild cracking of reduced crude, is charged through a line I to a furnace 2 or other suitable means'forraisirig the feed stock. to the temperakture desired for cracking. A diluentvis VchargedV through a liner3 to the furnace 2. A portion of this diluent Ymay be premixed with the charge stock throughV avalve V4in order to suppress thermal cracking and additional amounts ofthe dilu- Vent, heated in the furnace to the desired temperature,-are usually addedthrougha line 6 to the VVheated` gasr oil ina line 5 aheadV of a reaction chamber- I. This amount of diluent to be added in.' thisway mayfbedetermined by calculation of theamount ofl heat necessary for the endother- V rnicjrea'ction. Thediluent is preferably steam although in vthefirst'sta'ge hydrocarbon gases such butane and/ or lighter gases including theV refractory light gases produced in the cracking revaction' may .bel used. vTheY reaction chamber I maybe any one of` a number of known catalytic reactorsV employed Yin the industry. However, as

theinvention is concerned'primarily with a certain combination of process steps rather than 4with the designrof any particular piece of equipment; no attempt will be made Yto describe in detail the-various reaction chambers which'may be employedin Ycarrying `out theprocess. A reactor which may beemployedto good advantage, however, 4isv a multiple-bed type catalyst chamber Yprovided with suitable means for `injecting diluentsi to'be used as heat carriers at spaced points /in the direction of vapor flow.' It is not intended,

however, that the invention should be limited to this particular type of reactor.

The" reaction mixture leaves the catalyticV reactor I and'passes with cooling, which may be effected by any appropriate means, through a line 8 into a separator 9 in which the heavy residues and tar areseparated and removed at Ill. Vapors from theseparator pass through a line II and into a fractionator I2 where a further separation ofV heavy products and unconverted gas cil is effected.' The liquid products from the fractionator are withdrawn through all-he l@ While the vapors are taken overhead through a line I4 and admitted into a stabilizer l which is operated u Y, A The products withdrawn from stabilizer I5 by 1'0":

:way of a discharge line II constitute the feed stockof hydrocarbons of gasoline boiling range forthesecond-stage catalytic operation. A gasop line from an extraneous source such as that produced byfthermal or catalytic reforming or dehy- 5.; drogenation withA properties substantially similar Ystock added Vshould be carefullyvchosen to'avoid any'undesirable alteration' of the properties of the-principal feed stock component.

The charge" stock for the second-stage catalytic` operation flows through a line I8 and'is heated to the desired-temperature by heat-ex'- in the second stage is particularly desirable to` reduce coke'formation in furnace coil and catalytic reactor and as an aid in controlling tem- The quantities requiredmay be substantially smaller "than those" preferred vin the first stage catalytic treatment because of the overall exothermic nature of the reactions occurring in the second stage.

Upon' leaving thefrnace, the hot reaction mixture is takenthrough line"22 tothecatalyst chamber24in which'the'secondipha'se catalytic treatment occurs. The products from the reactor pass with Vsuitablecooling-'through a line 25 to a fractionator and/or separatornf in which the heavy products are removed through a line 2'IVV and the gaseous products and light gasoline are taken overhead to `a stabilizer v3l) through a line 29. A sidecuto'f heavy gasoline may in some cases be taken off'and returned 'as recycle through a line '28.4 The light gases are Withdrawn'v overhead from the stabilizer and may be subsequently used for polymerization and al'kylation While the gasoline is withdrawn frommthe bottom through line 32, This gasoline may be further fractionated to recover aviation-'fuel blending stock, motor fuel, and, if desired, may ber-subjected to closer fractionation and 'subsequent extraction of pure benvzene and/or toluene.

The operating conditions which may be employed to carry out successfully the process of the invention are approximately as follows:

The first stage operation may utilize as a feed 'stock ay petroleum distillate'of relatively wide boilingrangesuchas'a gas oil ornaphtha which may boil, for example, fromr about 400 to '700 F. The catalytic cracking operation may be carried out under moderately superatmospheric pressures varying from atmospheric pressure up to 200 per ton of catalyst. Steam or other suitable materials may be used as diluent and as heat carrier media. The first stage catalyst is an alumina base material which may be of either natural or synthetic origin. While the natural mineral bauxite is the preferred catalyst, synthetic alumina catalysts, either alone or with added activating materials such as various metal oxides, or in silica-alumina compositions, may be employed. The natural catalysts such as bauxite, activated clays and the like are ordinarily preferred because of their low cost and rugged characteristics.

I'h'e gasoline product obtained in the first stage possesses certain characteristics including high carbon-to-hydrogen ratio which make desirable its use as the charge stock to the second-stage operation. This gasoline is preferably of a relatively narrow boiling range such as that portion boiling in the approximate range of about 150 to about 400 F. Higher and/or lower boiling portions of the catalytically cracked gasoline products may be included in the feed stock if desired. However, the lower-boiling portions may not contribute greatly to the production of aromatics while the higher boiling portions may introduce difliculties due to increased carbon deposition and higher proportions of olens in the final product. While this catalytic gasoline comprises the preferred feed stock for this second stage, minor proportions of extraneous stocks of similar characteristics may be included satisfactorily.

The catalyst employed in the second-stage catalytic treatment is of the same general type as that used in the first stage, having an alumina base and being of either natural or synthetic origin. As in the first stage, bauxite is the preferred catalyst although other catalysts familiar to those versed in the art may be used.

The conversion reaction of the second stage is preferably carried out at a somewhat higher temperature than that employed in the first stage, temperatures in the region of about 1050 to about l250 F. being recommended. Moderately superatmospheric pressures such as from atmospheric to 200 pounds per square inch', are used and the flow rate may vary depending upon the degree of conversion desired. A diluent preferably steam may be used to control the temperature in the catalytic reactor during the exothermic reaction.

In order to indicate the novelty and utility o-f the process, the following example is given of one specific operation of the process as it may be accomplished in an apparatus such' as illustrated and above described when using the preferred catalyst and the preferred conditions of temperature and pressure. The example is merely illustrative of What may be accomplished and should not be construed as a limiting feature of the invention, for various other catalysts well known to those versed in the art may be employed within the broad scope of the invention and the operating conditions with each' of these catalysts adjusted to produce the desired result.

A gas oil stock of 35.6 API gravity and 400 to 700 F. boiling range was charged to a catalytic cracking unit utilizing bauxite catalyst. The gas oil charge was vaporized, admixed with superheated steam to give an oil-steam weight ratio of 2:1 and passed through the catalyst chamber at theapproximate range of about 900 to about 1100o F. depending on the charge stock. Flow rates vmay vary from 2 to 8 barrels of gas oil per hour 6 an average catalyst temperature of 1010 F. and 35 pounds gage pressure. The gas oil feed rate was approximately 6 barrels per ton of catalyst per hour and the average per pass conversion during a three hour processing period was 50 per cent by weight of the charge.

The cracked products were first separated from unconverted gas oil, and the 400 F. end point gasoline recovered amounted to about 30 Weight per cent of the gas oil charged. The C3-C'5 fraction of the gaseous products amounted to about 13 weight per cent of the charge and contained about '75 weight per cent of propylene, butylenes and amylenes for alkylation feed. The pentane-free gasoline was then fractionated to produce over volume per cent of a stock with a boiling range of 160 to 400 F. and a bromine number of about 70 which was charged to the second catalytic treatment.

The cracked gasoline was mixed with superheated steam to produce an oil-steam weight ratio of 6:1 and preheated to 1100 F. prior to contact with the catalyst. The gasoline was charged at a rate of 5 barrels per ton of catalyst per hour during a threehour processing period and the pressure was pounds gage.

The reaction products were cooled to separate small quantities of high-boiling material from the gasoline and lighter products, and the gasoline vapors were condensed and stabilized for the removal of C5 and lighter hydrocarbons. The

Cs-Ct hydrocarbon fraction amounted to ap-v proximately 16 weight per cent of the gasoline charged and contained 70 Weight per cent of the corresponding olefins. Pentane-free gasoline up to 400 F. end point amounted to over 70 Weight p-er cent of the gasoline charged. Refractionation of the gasoline product yielded a 160 to 200 F. fraction (benzene concentrate) containing over 50 Weight per cent of benzene and a motor fuel fraction consisting of material boiling below 200 F. after benzene extraction and material boiling above 330 F. The centercut aviation blending stock had a bromine number of 5 and contained over '75 weight per cent of aromatics.

We claim:

l. In a hydrocarbon conversion process for the production of a motor fuel of improved quality, of low olefin and high aromatic hydrocarbon content, the steps comprising introducing a stream of hydrocarbon oil boiling within the approximate temperature range of 400 to '700 F. into a closed zone Where the same is cracked at a temperature within the range of about 900 to 1100 F. in admixture with superheated steam to furnish endothermic heat of conversion, in the presence of a solid bauxite catalyst, said hydrocarbon oil being passed through said closed Zone at the rate of about 2 to 8 barrels of oil per ton of catalyst per hour, recovering unconverted and relatively heavy hydrocarbon material from the eiiluent of the preceding step, recovering a gasoline stock having a relatively high olen content and boiling in the range of about to 400 F. from said effluent, transmitting a stream of the gasoline stock into a second closed zone wherein the same is subjected to exothermic aromatization conditions at a higher temperature than in the cracking step in the range of about 1050 to 1250 F. admixture with steam diluent to control the exothermic aromatization conversion in the presence cf a catalyst comprising solid bauxite, said gasoline stock being passed through said second closed zone at the rate of about 5 barrels per ton of catalyst per hour, and obtaining therefrom Y "7 a vhydrocarbon ,material -of enhanced `antiknock characteristics, of'loW olefin content and Within the gasoline -boiling'range from the veiluent of the ysecond closed Zone.

2. `In a hydrocarbon Ycon-version process `for the production of a motor fuel of improved quality, of low olenand `high aromatic hydrocarbon content, the steps comprising introducing a stream of hydrocarbon oil boiling Within the approximate temperature range lof 400 to 700 F. into a closed .Zone where the same isV cracked at a temperature within the range of about 900 to 1100D F, in admixture Wit-h superheated steam v-to furnish endothermic heat of conversion, in the presence of a solid alumina catalyst, said hydrocarbon oil .being `passed through said closed zone at the rate of about 2 to 8 barrels .ofv oil Yper ton 'of catalyst per hour, recovering unconverted and relatively heavy hydrocarbon materialffrom vthe eilluent of the preceding step, recovering a gaso- `line stock having a relatively high olefin content and boiling in the range of about 150 to 400 F. from said eliluent, transmitting a streamof the gasoline stock intoy a .second closed Zone wherein the same is subjected to exothermic aromatization conditions at :a higher temperature than in the cracking step in the range of about 1050 to 250 F. in admixture With steam diluent to control the exothermic aromatization conversion in lthe presence of a catalyst comprising solid alumina, said .gasolinefstock :being passed v f/h-1, )i1gl1 `said vsecond closed zone at therate -obouti barrels per ton of kcatalyst,per hour, and obtain- :mg therefrom a vhyd-rocarbon material 1of -enhanced antiknock characteristics, of low iolen content and within the ,gasoline `bo-ling'range from the veiliuent ,ofl 1the ,second closed zone.

WAL'1'ERA-SC f E. vCARL J. HELMERS REFERENCES cum) 4The following refierenoesware oirecordEi-n L-1e file of this patenti:

UNITED STATES 4APA'IETNTS Thomas Sept. 26, :11944 

